1. Field of Invention
The present invention relates to a boring machine for producing tunnels or the like.
2. Description of Related Art
Conventional machines used for tunnel boring have a rotating cutter head mounted on heavily loaded bearings. Material removed by the cutter head during the boring operation passes rearwards for removal from the face of the cutter.
A problem with these conventional boring machines is that some of the material removed in the cutting operation penetrates the bearing seals and contaminates the bearings. Debris contamination of the bearing reduces the performance of the reliability of the bearings.
Conventional hydrostatic bearings have bearing fluid distributed to the bearing surfaces via a recess, the recess also acting as a restrictor. U.S. Pat. No. 3,917,366 to Mason discloses a hydrostatic bearing having these features. However, Mason does not teach the use of an expendable bearing medium nor the use of pressurized water as an expendable bearing medium.
The advantage of using an expendable bearing medium is that no filtration system is required and the bearing medium prevents the ingress of contaminants into the bearings. Further, using pressurized water as the expendable bearing medium has the advantage that it acts as a fire retardant and is biodegradable.